To call Allah is called ‘dua’. To call an individual/ creation is called ‘neda’. To call an individual/ creation may be or may not be ‘Shirk’.
In terms of ownership, everything contained in/ belonging to this universe is owned by Allah. But ownership may be further divided into two types. First is such ownership which exclusively belongs to Allah (e.g. life; death; ‘hidayat’; ‘gumrahi’ etc.); second is such ownership which may also belong to individuals (e.g. wealth; employment; goods etc.).
Shirk is actually relating to subject-matter of the call, and the intention of the caller. If the subject-matter of call is something exclusively owned by Allah, such a call to an individual/ creation will be ‘shirk’, if the intention of the caller is that the individual called out will not make a ‘dua’ to Allah for fulfillment of the caller’s request. If the subject-matter of the call is something whose ownership may also belong to individuals, such a call to an individual/ creation will not be ‘shirk’, if the caller’s intention is that the individual called out may get the caller’s request fulfilled out of the resources owned/ managed by the person called out; OR that, if such resources are not available to the person called out, the person called out will make a ‘dua’ to Allah for fulfillment of the caller’s request.
A ‘neda’ constituting a ‘shirk’ is also called ‘dua’ to individual/ creation.